Well, about Vampires walking in daylight: Dracula could do this too. He just didn't sparkle.
It's often been my interpetation that vampires could walk around in daylight they just couldn't be in direct sunlight
. In "Twilight" they live in Washington which, it seems, is in perpetual overcast.
But "classic" vampires to me, it seems, that they can be up in the daytime but direct sunlight kills them. I guess, um, the clouds scatter the sunbeams enough to not effect the vampires.